Is there any way to draw multiple images in a FlxSprite?

Hello! I’m new moved from GameMaker and having fun with HaxeFlixel. I’m Japanese, Sorry for my bad English. ;(

I have two Images overlapped in the screen and want to change their alpha.

But like this:
Not like this:

I placed them in a FlxSpriteGroup as a FlxSprite, But it didn’t work (I didn’t think it works...).

In GameMaker, I normally made a surface and placed all sprites in there, then set the surface’s alpha. But It seems doing something on draw() is not a thing to do on Flixel.
Is there any way to do this?